BayCEER Workshop 2026

Apomixis supports niche edge adaptations in Sorbus

1.1 in Morning Session

08.10.2026, 11:15-11:30, H 36

Seed reproduction without recombination (apomixis), particularly in combination with hybrid speciation, is increasingly recognized as a developmental strategy rather than an evolutionary dead end. In this study, we investigate whether apomictic lineages in the genus Sorbus can preserve adaptations at the margins of parental ecological niches.
To examine niche differentiation among apomictic entities of hybrid origin, we focused on Sorbus subgenus Aria in the Franconian Jura, Bavaria. We quantified niche space by calculating two-dimensional hypervolumes for triploid entities and their diploid and tetraploid parental species, Sorbus aria and S. collina. The triploid offspring comprised five genetically and morphologically distinct groups (entities), one group characterized by a consistent morphotype but divergent genetic background, suggesting a polytopic origin, as well as individuals with unique morphology and high genetic heterogeneity, referred to as “single genotypes”.
For the analysis of niche overlap, we selected four environmental variables with the highest contribution in PCA and used them to construct the hypervolumes. Hypervolume comparisons revealed significant differences between nearly all triploid entities, single genotypes, and their parental taxa.
In three cases, environmental niche space extended beyond the parental hypervolume margins, while in one case it was significantly shifted toward the margins. In the remaining cases, niches were intermediate. Niche transgression beyond parental ranges occurred toward milder temperatures and drier conditions.
Although triploid Sorbus taxa are facultatively apomictic, they may still allow for gene flow into parental lineages. We therefore propose that apomictic lineages can act as reservoirs of adaptive variation. Over long time scales, conserved and novel trait combinations may re-enter the parental gene pool via introgression, thereby reintroducing adaptations critical for survival under rapidly changing conditions, promoting further speciation.

Triploid, apomictic Sorbi endemic to boulder-rich, calcerous sites throughout Europe may act as genetical reservoirs for adaptive variation while growing at and beyond the parental niches.

Keywords: Hybrid speciation, Apomixis, Niche evolution, Transgression, Polyploidy Sorbus

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